The research proposed herein seeks an understanding of the role of the visual climbing fiber (CF) pathway to the flocculus of the cerebellum in the control of eye movement. The technique of extracellular single unit recording will be used to record the activity evoked in single floccular Purkinje cells by optokinetic (OKN), neck proprioceptive, and vestibuloocular reflex (VOR) activation, in unanesthetized rabbits. The visual stimulus will be servo-controlled by feed-back of eye position so that the retinal slip velocity of the OKN stimulus can be "clamped". The possible role of CF evoked Golgi cell inhibition in cerebellar function will be examined. The effect of constant retinal slip velocity on the activity of cells in the medial vestibular nucleus will be examined. The parameters of OKN stimulation which induce long term changes in the VOR will be specified both behaviorally and electrophysiologically. The technique rapid autoradiography (RARG) will be used to study the spatial distribution of CF projections to the flocculus. The histochemical stain of 5'nucleotidase and the RARG technique will be used to study modification of staining patterns in the flocculus as a consequence of OKN constant retinal slip velocity stimulation and as a consequence of compensation following unilateral destruction of a horizontal semicircular canal. The influence of binocular visual deprivation of extraocular muscle stiffness will be studied in kittens. The influence of binocular visual deprivation of extraocular muscle stiffness will be studied in kittens. The influence of modification extraocular muscle proprioceptive input on eye position control during VOR activation will be examined.